The present invention relates generally to power and control systems for micro-electronics. More particularly, it concerns a battery, power management and control system therefor that features a high-power, long-life switching mode power supply compatible with various battery chemistries and an associated controller for supplying relatively short-term high-current switchable primary and relatively long-term low-current standby DC power in a volume-restricted space such as that of electrochromic (EC) eyewear. In a dual lead-acid battery configuration, an external battery charger integral with an EC eyewear case is provided. The invention also involves a unique temple including a leaf spring hinge assembly and a protective temple tip coating useful for eyewear generally.
Currently available electrochromic (EC) eyewear is characterized by long transmissivity switching times, short operating (e.g. battery) life and a bulky frame that reduce its aesthetic appeal. The invention represents a broad-based approach to solving various problems with power supply and controller microelectronics to achieve greatly improved switching times, longer and more stable operation and consumer demands for more aesthetic and lightweight frames. It does so with various battery chemistries having form factors compatible with eyewear temples, with micro-miniaturized power supply and controller electronics having a form factor compatible with eyewear bridges, with signal distribution and switching via flex circuitry, with improved hinges connecting temples and eyewires, with lens-protective temple tip coatings and with an external battery charger case for convenient recharging of lead acid cells in one battery configuration.
Hybrid battery systems are not new. U.S. Pat. No. 4,770,954 describes a switching power supply having two battery types in a hybrid arrangement having their positive output terminals connected in parallel through common-cathode connected diodes to supply an output voltage alternatively from either a high-energy density source or a low-energy density source. The sources are said to be lithium-type and zinc-silver oxide-type. U.S. Pat. No. 4,977,899 describes a dual-battery system for use in lightweight, portable electrocardiograph (ECG) monitoring devices also have been proposed. A lithium battery provides reduced-voltage level to sustain a volatile read-and-write memory (RAM) device over the long life of the monitor while triple, series-connected replaceable/rechargeable alkaline batteries provide primary power to circuit elements for a short term of high-demand ECG data monitoring and recording. U.S. Pat. No. 4,883,728 describes a lead acid automotive battery that meets diverse current requirements by providing cells having different electrode thicknesses.
It has been determined that use of a primary cell alone cannot best meet certain pulse power drain demands placed, for example, on commercially available silver oxide "button" batteries (such as those used in watches and some pocket cameras) or lithium cells having a small form factor. This is because of high internal resistance in such batteries that leads to internal losses during pulse discharge, and the danger of damage when such batteries are over-driven.
The invention in a first embodiment solves this problem by using dual silver oxide batteries, in another by using dual lead acid batteries and in yet another by using dual lithium/thionyl chloride batteries. The invention in still another embodiment solves this problem by using the lower internal resistance of a lead acid cell secondary battery to provide the pulse rate requirements, while using a lithium-type cell primary battery to provide the needed capacity for long life. The invention in these various embodiments includes a controller that accommodates any of the various battery combinations and provides the needed switching currents and voltages to meet the demanding EC eyewear switching and lifetime requirements.
Briefly summarizing the merits of the various embodiments, the invented system preferably includes a primary, lithium-type cell and a secondary, sealed lead acid cell in a hybrid, power-sharing configuration capable of supplying the relatively low-energy high-current (pulse) drain and relatively high-energy, low-current requirements, for example, of a switchable EC lens, while providing high operating cycle life and shelf life. A switch-mode power supply controller manages the power-sharing load on the hybrid batteries such that the secondary cell is charged by the primary cell. The system is capable of meeting the demanding EC short-term lens pulse drain requirements of approximately 60-130 milliamps (mA) for five to ten seconds (required to switch EC lenses from clear to fully darkened at an acceptably fast rate) and the long-term life requirements of over two thousand cycles. The invented lead acid battery provides approximately 12-15 mA-hours' capacity and the invented lithium-type battery provides nearly 180 mA-hours' capacity, all in a tiny volume of approximately one milliliter (1 ml) that is fittable, for example, within voids formed in either of the frame members of eyeglasses. Preferably, the lithium-type and lead acid-type batteries are of approximately equal form factor and volume, for symmetric placement thereof in such volume-restricted spaces.
In the dual lithium/thionyl chloride battery subsystem, a nominal 3.65 volts (3.65 V) output of the dual, parallel-connected lithium-type batteries (each approximately 35 mm long) is converted down to a maximum potential of 2.2 V at sufficiently higher current that rapidly switching the EC lenses is possible. In the dual lead acid battery subsystem, in which the batteries are connected in series, a nominal 4 V output of the batteries is used by a lens driver circuit to drive the EC lenses at a high switching current that characterizes the lead acid cells, and an external battery charger case provides for convenient, periodic recharging of the lead acid cells. In the dual or quad silver oxide battery subsystem, two to four batteries are operated in series and/or parallel nominally to to supply 4 V at up to approximately -150 mA .ltoreq.I +150 mA. Accordingly, the best characteristics of each of the cell types flexibly are accommodated in various form factors and with various lifetimes that are compatible with a wide range of EC eyewear and similarly demanding applications.
The invented system in its preferred embodiment thus integrates the better properties of lithium-type and lead acid-type cells in a hybrid arrangement that also avoids their known shortcomings. The invented system provides unprecedented long life via the primary cell and unprecedented high switching capacity via the secondary cell in an unprecedented small volume. This advantageous characteristic of the invented system in its preferred embodiment will be referred to herein as high energy density. In the alternative embodiments, the voltage/current characteristics and capacities of various paired cell-types are optimized for EC eyewear switching applications, some of them focused on extending useful battery life, others focused on avoiding battery recharge requirements, yet others focused on reducing battery replacement cost and still others focused on minimizing frame and temple size for aesthetic reasons.
Other aspects of the invention include the provision of a unique hinge assembly, including a leaf spring defining an inner wall of a forward region of the battery tubes, connecting the eyewear's eyewires and each temple. They also include the provision in at least an inner region of the temple tips of a polymeric material for protecting the EC lenses when the temples are folded. Finally, they include the provision of an external battery charger case for supporting the EC eyewear and for charging relatively short-lived batteries, e.g. a lead acid pair, without disassembly of the eyewear and with a ultra-low-power annunciator to apprise the EC eyewearer of the charging status.
These and additional objects and advantages of the present invention will be more readily understood after a consideration of the drawings and the detailed description of the preferred embodiment.